While the XD221u will not cure the resin without modifications, the focus distance is too far and the curing time is too long at 15 seconds exposure per layer. The focus had to be modified for close distances and the UV filter had to be removed allow more UV light through. Making it cure the resin faster is easy, just remove the filter (glass square) on the front of the bulb. Making the projector focus at ≈7" was a bit more difficult. The service manual has been attached for assistance in dis-assembly if you are using an xd221u projector, but the modification should be similar for most projectors.
WARNING: I am not responsible for any damage, injury, blindness, death, etc. that may be inflicted upon you during these instructions. Your actions are your own and you should know what is and isn't safe to do. Use common sense and you will be fine.
Now for the fun part. The steps correspond roughly to in order of the pictures
Modifying the focus
1-3. Remove the bulb cover and bulb from the projector. There are two screws and two clips holing the bulb in.
4. Remove the 8 screws from the bottom of the projector
5-6. Remove the three screws holing the back plate on, and use a flat head screwdriver to remove the back plate.
7-9. Lift the top of the projector off being careful not to rip the ribbon cable connected to the top buttons. Lift the clip holding the cable to the motherboard and slide the cable free.
10-12. Remove the zoom adjustment piece by prying out the 2 clips holding it in. Then remove the zoom frame by screwing the two screws holding it in place.
(WARNING: for the next several steps do not touch any of the lenses or you will not be able to get a clear picture after you are done.)
13-14. Remove the four screws holding the focus lens assembly in place, there is very little room for a normal screwdriver here, I had to use pliers and a Philips piece from a multi-head screwdriver. To remove and replace these.
15. Turn the assembly upside down and rotate the focus lens outward until its stops, inspect the circumference of the body of the focus assembly and you should see a very small screw that is screwed into the focus lens housing and is colliding with the outer assembly case. This is the screw that prevents the lens from unscrewing too far.
Remove this screw. You will now be able to turn the lens farther to focus at a closer distance. (WARNING: removing this screw allows the focus lens to be unscrewed all the way and fall out of the projector if turned too far, be aware of this as you focus the projector)
16. Re-assemble the projector but don't put the bulb in yet. Reverse the steps used to disassemble. The lens can now turn far enough to focus at close distances, which is needed for high resolution prints.
16-18. For the xd221u, there is a tab on the focus lens that will prevent the lens from turning to far, this is both good news and bad news. the good news is that I can use this to prevent the lens from falling out if it gets turned too far, the bad news is that the lens still can't turn far enough to focus at the distance I was looking for. To fix this use a file and slowly file down the tab until there is 1-2mm of distance from the tab to the projectors case.
I found that the lens will fall out when turned to around 300° (looking head on with 0° at the right) so I super-glued a scrap piece of scrap plastic to the case about 5mm from the point the lens will fall out to stop the lens from turning too far. This gives me a focus distance of approximately 6.75 inches from the front of the projector and a projection area of 4in wide by 3in tall.
Modifying the bulb - Then I needed to remove the UV filter to make the layers cure quicker.
19. If you are at the right angle you can see the square piece of glass at the front of the bulb that is the UV filter.
20. Remove the screw holding the metal plate on.
21-22. Use a small flat head to pry the metal clips out and up.
23. Remove the UV filter by lifting the glass out or by tilting the bulb until it falls out into your hand.
24. keep the UV filter in a safe and protected place, if you ever want to use the projector to watch movies or play games on, you will need to put the filter back in.
Put the bulb back in to projector, and turn it on. If everything works, well done! if not, open it up make sure that the ribbon cable for the buttons is attached correctly, no other cables were disconnected, and that the circuit board didn't suffer any damage. Connect a video source. Turn the focus as far as it will go without falling out, use a piece of paper or the wall to measure a rough estimate of the focal distance, this will be fine-tuned after it is attached to the printer.